First steps

First, create a new directory, and use wrangler, our command line tool for building Cloudflare Workers, which we assume you have installed already, to initialize the project:

mkdir openapi-example && cd openapi-example
wrangler init

And install itty-router-openapi

npm i @cloudflare/itty-router-openapi --save

Then in the src/index.ts place this, the smallest router you can have in itty-router-openapi.

import { OpenAPIRouter } from '@cloudflare/itty-router-openapi'

const router = OpenAPIRouter()

export default {
  fetch: router.handle,
}

Now when running wrangler dev you see server logs

wrangler dev
⛅️ wrangler 3.4.0
------------------
wrangler dev now uses local mode by default, powered by 🔥 Miniflare and 👷 workerd.
To run an edge preview session for your Worker, use wrangler dev --remote
⎔ Starting local server...
⎔ Reloading local server...
[mf:inf] Ready on http://127.0.0.1:8787/
[mf:inf] Updated and ready on http://127.0.0.1:8787/

You can now open http://127.0.0.1:8787/docs in your browser to see the Swagger UI, that will hold your future endpoints.

// TODO screenshot /docs

You can also open the http://127.0.0.1:8787/redocs to see an alternative version with the same endpoints.

// TODO screenshot /redocs

Creating your first endpoint

This is the simplest endpoint you can create, that don't receive any parameters, neither have a response format defined.

import { OpenAPIRoute } from '@cloudflare/itty-router-openapi'

export class ListEndpoint extends OpenAPIRoute {
  async handle(request: Request, env: any, context: any, data: any) {
    return ["cloudflare", "workers"]
  }
}

After this you must register the endpoint in the initial router, so your src/index.ts should look something like this:

import { OpenAPIRouter } from '@cloudflare/itty-router-openapi'

const router = OpenAPIRouter()
router.get('/list/', ListEndpoint)

export default {
  fetch: router.handle,
}

Now when opening the /docs you will see your new endpoint and be able to test it right away.

// TODO screenshot /docs with endpoint